International Journal of Number Theory, vol.18, no.3, pp.473-484, 2022 (SCI-Expanded)
© 2022 World Scientific Publishing Company.Let d be a positive square-free integer and d = (Td + Udd)/2 > 1 be the fundamental unit of the real quadratic field ℚ(d). The Ankeny-Artin-Chowla (AAC) conjecture asserts that Up≢0 (mod p) for primes p 1 (mod 4), which still remains unsolved. In this paper, sufficient conditions for Ud < d have been given in terms of Yokoi's invariants nd and md, and it has been shown that the AAC conjecture is true in some special cases.